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[PATCH v5 10/11] cpuidle/powernv: Add support for POWER ISA v3 idle states

From "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject [PATCH v5 10/11] cpuidle/powernv: Add support for POWER ISA v3 idle states
Date 2016-06-02 14:40 +0200
Message-ID <rFA4N-5VV-23@gated-at.bofh.it> (permalink)
References <rFA4N-5VV-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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POWER ISA v3 defines a new idle processor core mechanism. In summary,
 a) new instruction named stop is added.
 b) new per thread SPR named PSSCR is added which controls the behavior
	of stop instruction.

Supported idle states and value to be written to PSSCR register to enter
any idle state is exposed via ibm,cpu-idle-state-names and
ibm,cpu-idle-state-psscr respectively. To enter an idle state,
platform provided power_stop() needs to be invoked with the appropriate
PSSCR value.

This patch adds support for this new mechanism in cpuidle powernv driver.

Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: linux-pm@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxppc-dev@lists.ozlabs.org
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
---
Note: Documentation for the device tree bindings is posted here-
http://patchwork.ozlabs.org/patch/629125/

Changes in v5
=============
 - Use generic cpuidle constant CPUIDLE_NAME_LEN
 - Fix return code handling for of_property_read_string_array
 - Use DT flags to determine if are using stop instruction, instead of
   cpu_has_feature
 - Removed uncessary cast with names
 - &stop_loop -> stop_loop
 - Added POWERNV_THRESHOLD_LATENCY_NS to filter out idle states with high latency

 drivers/cpuidle/cpuidle-powernv.c | 71 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 3a763a8..0717dc6 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -20,6 +20,8 @@
 #include <asm/opal.h>
 #include <asm/runlatch.h>
 
+#define POWERNV_THRESHOLD_LATENCY_NS 200000
+
 struct cpuidle_driver powernv_idle_driver = {
 	.name             = "powernv_idle",
 	.owner            = THIS_MODULE,
@@ -27,6 +29,9 @@ struct cpuidle_driver powernv_idle_driver = {
 
 static int max_idle_state;
 static struct cpuidle_state *cpuidle_state_table;
+
+static u64 stop_psscr_table[CPUIDLE_STATE_MAX];
+
 static u64 snooze_timeout;
 static bool snooze_timeout_en;
 
@@ -91,6 +96,17 @@ static int fastsleep_loop(struct cpuidle_device *dev,
 	return index;
 }
 #endif
+
+static int stop_loop(struct cpuidle_device *dev,
+		     struct cpuidle_driver *drv,
+		     int index)
+{
+	ppc64_runlatch_off();
+	power_stop(stop_psscr_table[index]);
+	ppc64_runlatch_on();
+	return index;
+}
+
 /*
  * States for dedicated partition case.
  */
@@ -167,6 +183,8 @@ static int powernv_add_idle_states(void)
 	int nr_idle_states = 1; /* Snooze */
 	int dt_idle_states;
 	u32 *latency_ns, *residency_ns, *flags;
+	u64 *psscr_val = NULL;
+	const char *names[CPUIDLE_STATE_MAX];
 	int i, rc;
 
 	/* Currently we have snooze statically defined */
@@ -199,12 +217,41 @@ static int powernv_add_idle_states(void)
 		goto out_free_latency;
 	}
 
+	rc = of_property_read_string_array(power_mgt,
+					   "ibm,cpu-idle-state-names", names,
+					   dt_idle_states);
+	if (rc < 0) {
+		pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-names in DT\n");
+		goto out_free_latency;
+	}
+
+	/*
+	 * If the idle states use stop instruction, probe for psscr values
+	 * which are necessary to specify required stop level.
+	 */
+	if (flags[0] & (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP)) {
+		psscr_val = kcalloc(dt_idle_states, sizeof(*psscr_val),
+				    GFP_KERNEL);
+		rc = of_property_read_u64_array(power_mgt,
+						"ibm,cpu-idle-state-psscr",
+						psscr_val, dt_idle_states);
+		if (rc) {
+			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
+			goto out_free_psscr;
+		}
+	}
 	residency_ns = kzalloc(sizeof(*residency_ns) * dt_idle_states, GFP_KERNEL);
 	rc = of_property_read_u32_array(power_mgt,
 		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
 
 	for (i = 0; i < dt_idle_states; i++) {
-
+		/*
+		 * If an idle state has exit latency beyond
+		 * POWERNV_THRESHOLD_LATENCY_NS then don't use it
+		 * in cpu-idle.
+		 */
+		if (latency_ns[i] > POWERNV_THRESHOLD_LATENCY_NS)
+			continue;
 		/*
 		 * Cpuidle accepts exit_latency and target_residency in us.
 		 * Use default target_residency values if f/w does not expose it.
@@ -216,6 +263,16 @@ static int powernv_add_idle_states(void)
 			powernv_states[nr_idle_states].flags = 0;
 			powernv_states[nr_idle_states].target_residency = 100;
 			powernv_states[nr_idle_states].enter = &nap_loop;
+		} else if ((flags[i] & OPAL_PM_STOP_INST_FAST) &&
+				!(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
+			strncpy(powernv_states[nr_idle_states].name,
+				names[i], CPUIDLE_NAME_LEN);
+			strncpy(powernv_states[nr_idle_states].desc,
+				names[i], CPUIDLE_NAME_LEN);
+			powernv_states[nr_idle_states].flags = 0;
+
+			powernv_states[nr_idle_states].enter = stop_loop;
+			stop_psscr_table[nr_idle_states] = psscr_val[i];
 		}
 
 		/*
@@ -231,6 +288,16 @@ static int powernv_add_idle_states(void)
 			powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
 			powernv_states[nr_idle_states].target_residency = 300000;
 			powernv_states[nr_idle_states].enter = &fastsleep_loop;
+		} else if ((flags[i] & OPAL_PM_STOP_INST_DEEP) &&
+				(flags[i] & OPAL_PM_TIMEBASE_STOP)) {
+			strncpy(powernv_states[nr_idle_states].name,
+				names[i], CPUIDLE_NAME_LEN);
+			strncpy(powernv_states[nr_idle_states].desc,
+				names[i], CPUIDLE_NAME_LEN);
+
+			powernv_states[nr_idle_states].flags = CPUIDLE_FLAG_TIMER_STOP;
+			powernv_states[nr_idle_states].enter = stop_loop;
+			stop_psscr_table[nr_idle_states] = psscr_val[i];
 		}
 #endif
 		powernv_states[nr_idle_states].exit_latency =
@@ -245,6 +312,8 @@ static int powernv_add_idle_states(void)
 	}
 
 	kfree(residency_ns);
+out_free_psscr:
+	kfree(psscr_val);
 out_free_latency:
 	kfree(latency_ns);
 out_free_flags:
-- 
2.1.4

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[PATCH v5 00/11]  powerpc/powernv/cpuidle: Add support for POWER ISA v3 idle states "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 09/11] cpuidle/powernv: Use CPUIDLE_STATE_MAX instead of MAX_POWERNV_IDLE_STATES "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 11/11] powerpc/powernv: Use deepest stop state when cpu is offlined "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 02/11] powerpc/kvm: make hypervisor state restore a function "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 10/11] cpuidle/powernv: Add support for POWER ISA v3 idle states "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 06/11] powerpc/powernv: abstraction for saving SPRs before entering deep idle states "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 05/11] powerpc/powernv: Make pnv_powersave_common more generic "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:40 +0200
  [PATCH v5 03/11] powerpc/powernv: Rename idle_power7.S to idle_power_common.S "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:50 +0200
  [PATCH v5 07/11] powerpc/powernv: set power_save func after the idle states are initialized "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:50 +0200
  [PATCH v5 08/11] powerpc/powernv: Add platform support for stop instruction "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:50 +0200
    Re: [PATCH v5 08/11] powerpc/powernv: Add platform support for stop  instruction Benjamin Herrenschmidt <benh@au1.ibm.com> - 2016-06-06 00:30 +0200
      Re: [PATCH v5 08/11] powerpc/powernv: Add platform support for stop  instruction Shreyas B Prabhu <shreyas@linux.vnet.ibm.com> - 2016-06-08 19:10 +0200
        Re: [PATCH v5 08/11] powerpc/powernv: Add platform support for stop  instruction Michael Neuling <mikey@neuling.org> - 2016-06-09 00:30 +0200
    Re: [PATCH v5 08/11] powerpc/powernv: Add platform support for stop  instruction Sam Bobroff <sam.bobroff@au1.ibm.com> - 2016-06-09 06:50 +0200
      Re: [PATCH v5 08/11] powerpc/powernv: Add platform support for stop  instruction Shreyas B Prabhu <shreyas@linux.vnet.ibm.com> - 2016-06-09 18:10 +0200
  [PATCH v5 01/11] powerpc/powernv: Use PNV_THREAD_WINKLE macro while requesting for winkle "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:50 +0200
  [PATCH v5 04/11] powerpc/powernv: Rename reusable idle functions to hardware agnostic names "Shreyas B. Prabhu" <shreyas@linux.vnet.ibm.com> - 2016-06-02 14:50 +0200

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